Actually, I called Yale two mornings ago (Tuesday, 26th) and the receptionist said they were still working on them and we should hear soon.
According to this website, some acceptances have been sent out, so she could have been lying, I suppose. But I also think it's possible that certain concentrations sent out their acceptances before others.
Columbia's notifications go through the GSAS front office, not through the department, according to one of my professors who was on the admissions committee in years past. As of last night, he had not heard any decisions had been finalized, but he's not on the committee any longer, so you can take that as you will. The GSAS office, and Columbia in general, are notoriously unorganized though. So even if decisions have been made, I would be surprised if we heard anything this week.
Good luck to everyone.